Fabricating method of a silicon thin film and method for manufacturing a solar cell using the fabricating method

Abstract

A fabricating method of a Si thin film which has no grain boundaries, photo-absorption characteristics similar to those of monocrystalline Si, and a low electrical resistivity, is provided. When electron beams 14 are applied to a deposition material source 12 to deposit the Si thin film on a substrate 10, assist ions are applied from an assist ion source 18 in the direction normal to the surface of the substrate 10.

What is claimed is: 
     
       1. A fabricating method of a silicon (Si) thin film which is formed on a substrate by electron beam deposition during which assist ions are simultaneously applied, wherein the energy of the applied assist ions is in the range of 300 to 1500 eV, and an I/A ratio, a ratio of a number of applied assist ions to a number of deposited Si atoms, is in the range of 0.2 to 1.1.   
     
     
       2. A fabricating method of a Si thin film in accordance with claim 1, wherein the assist ions are argon (Ar) ions. 
     
     
       3. A fabricating method of a Si thin film in accordance with claim 1, wherein a glass substrate or a silicon substrate is used as the substrate. 
     
     
       4. A fabricating method of a Si thin film in accordance with claim 1, wherein a surface of the substrate on which a Si thin film is formed, is placed at an angle of 45 degrees to the straight line connecting a deposition material source and the substrate, and normal to the incident direction of the assist ions. 
     
     
       5. A method for manufacturing a solar cell comprising a Si thin film, wherein the Si thin film is fabricated by a fabricating method in accordance with claim 1. 
     
     
       6. A method for manufacturing a solar cell in accordance with claim 5, wherein the Si thin film is used for an i layer of a p-i-n type solar cell. 
     
     
       7. A method for manufacturing a solar cell in accordance with claim 5, wherein electrodes are disposed so that carriers move in parallel to the substrate. 
     
     
       8. A method for manufacturing a solar cell in accordance with claim 5, wherein phosphorus (P) is diffused in the Si thin film fabricated by a fabricating method in accordance with claim 1, when an n ++   layer is formed just under an electrode formed on a Si layer. 
     
     
       9. A method for manufacturing a solar cell in accordance with claim 5, wherein the Si thin film is fabricated on a p type silicon layer by a fabricating method in accordance with claim 1, and phosphorus (P) is diffused in the fabricated Si thin film in order to form a pn junction. 
     
     
       10. A method for manufacturing a solar cell in accordance with claim 5, wherein the bandgap of the Si thin film is continuously controlled by continuously varying at least one of the energy of the assist ions or the I/A ratio. 
     
     
       11. A method for manufacturing a solar cell in accordance with claim 5, wherein the solar cell has a tandem structure comprising three layers of the Si thin films, and the bandgaps of the Si thin films included in the three layers are different from each other.